The more contagious delta COVID-19 variant has been detected in nearly all of the positive tests sequenced in Maine in recent weeks, a situation likely to continue driving up the number of positive cases in the state, a top health official said Tuesday.

Maine Center for Disease Control and Prevention Director Nirav Shah said that figure poses serious challenges for the state as cases continue to rise, although Maine still has the lowest rates in the state.

The delta variant is more contagious and has been linked to more severe cases of illness. In July, it made up an estimated 86 percent of new cases in Maine. The state genetically sequences roughly 10 percent of positive tests to check for variants.

“It is not just the predominant variant in Maine, it is the variant in Maine,” Shah said.

Cases have been increasing in the last month, with the majority of those and hospitalizations being among unvaccinated people. The state’s high vaccination rate — Maine is the fourth-most vaccinated state in the country with 65 percent of the population having their final shot — is likely preventing the situation from getting worse as quickly as other states.

But that could change in the coming days. Shah said there are 1,700 positive test results received within the last 36 hours that the Maine CDC is waiting to review, which will likely result in a sharp uptick in detected cases within the coming days.